[Burnt Powder]

No cartridges, be them rifle, handgun, or shotgun have a linear relationship between powder quantity, projectie velocity, and pressure all the time. All do some of the time depending on a whole plethora of conditions.

As one example, depending on bullet weight and powder choice/burn speed, most any rifle chambering can reach a point where regardless of how much powder you pack in the case, you will not see an increase in velocity or pressure. In fact, it might go down and excess powder become ejecta rather than propellant. On the other hand, with a much faster burn rate powder you may experience a similar increase in velocity and pressure until you reach a certain point where the pressure spikes and you do not increase velocity, and this with only a very small increase in powder charge. Increase it just a little more and the pressure can increase exponentially!

Then you can use the correct burn rate powder, fill the case, obtain maximum velocity at manageable pressures. You have arrived! This is usually close to linear, parallel performance compared to powder charge, but not exact on either end of the scale.

All smokeless powders burn more efficiently under pressure. Typically the higher the pressure the faster the burn rate, the higher the pressure, the faster the burn rate, the higher...... It just spirals out of control quickly if proper procedures are not followed. Other powders are slow enough that the projectile will have exited the barrel venting the pressure before the increasing pressure and resulting increase in pressure and burn speed gets out of hand!

This is greatly effected by powder characteristics. It just isn't all that simple!

BP